ink_* -> ats_* in the "core" code

[Leif Hedstrom]

Hi all,

I'd like to propose that we start using ats_ as a prefix for new APIs 
(and rewrites etc.) in the internal code. Long term, we probably should 
migrate existing ink_ prefixes to ats_, and perhaps also consider using 
C++ name spaces.  My rationale for using "ats" instead "ts" in the 
internal (core) code is to make it easily distinguishable from the 
public APIs (which are all prefix e.g. TS or ts). This is very useful 
when grepping through the code IMO.

Cheers,

-- Leif